Bottom Line:
Two molecular markers, AFLPs and mitochondrial COI, were used to examine genetic variation among these regional populations and to compare the sequences with those available in GenBank and BOLD.We found geographic population structure in the southern United States which suggests two introductions and the presence of a previously unknown cryptic species.Management of D. saccharalis would likely benefit from further investigation of population genetics throughout the range of this species.

Affiliation: SNRI, University of California Merced, Merced, California, United States of America.

ABSTRACTThe sugarcane borer moth, Diatraea saccharalis, is widespread throughout the Western Hemisphere, and is considered an introduced species in the southern United States. Although this moth has a wide distribution and is a pest of many crop plants including sugarcane, corn, sorghum and rice, it is considered one species. The objective was to investigate whether more than one introduction of D. saccharalis had occurred in the southern United States and whether any cryptic species were present. We field collected D. saccharalis in Texas, Louisiana and Florida in the southern United States. Two molecular markers, AFLPs and mitochondrial COI, were used to examine genetic variation among these regional populations and to compare the sequences with those available in GenBank and BOLD. We found geographic population structure in the southern United States which suggests two introductions and the presence of a previously unknown cryptic species. Management of D. saccharalis would likely benefit from further investigation of population genetics throughout the range of this species.

pone-0110036-g002: Structure 2.2 analysis depicts two genetically distinct clusters of D. saccharalis.Individuals from southern Texas (S. Texas), eastern Texas (E. Texas) and Louisiana grouped together within the red cluster, while individuals from Florida grouped within the green cluster. The y-axis shows the probability of each individual to belong to a genetically distinct cluster. The number of individuals from each region used for the analysis is represented by ‘n’.

Mentions:
A total of 79 D. saccharalis male adults (18 from southern Texas, 13 from eastern Texas, 27 from Louisiana, and 21 from Florida) and two primer combinations (M-CAT/E-ACT; M-CAC/E-ACG) were used to obtain 96 AFLP markers. This number of individuals and markers were found to be sufficient in order to adequately represent population genetic structure of this insect in the sampled regions [39]. Structure 2.2 analyses clearly depict two genetically distinct clusters of D. saccharalis present in the southern United States (Figure 2). The presence of two distinct clusters was confirmed using the ΔK statistic of Evanno et al. [42]. Diatraea saccharalis from southern Texas, eastern Texas and Louisiana grouped together, whereas individuals from Florida belong to a genetically distinct cluster. Our data show no evidence of interbreeding or migration between the two genetic clusters, suggesting that the Florida population of D. saccharalis is a distinct genotype and possibly a cryptic species. Of the 96 alleles produced by the AFLP reactions, 24 were present only in Texas and Louisiana, while 14 alleles were unique to the Florida population.

pone-0110036-g002: Structure 2.2 analysis depicts two genetically distinct clusters of D. saccharalis.Individuals from southern Texas (S. Texas), eastern Texas (E. Texas) and Louisiana grouped together within the red cluster, while individuals from Florida grouped within the green cluster. The y-axis shows the probability of each individual to belong to a genetically distinct cluster. The number of individuals from each region used for the analysis is represented by ‘n’.

Mentions:
A total of 79 D. saccharalis male adults (18 from southern Texas, 13 from eastern Texas, 27 from Louisiana, and 21 from Florida) and two primer combinations (M-CAT/E-ACT; M-CAC/E-ACG) were used to obtain 96 AFLP markers. This number of individuals and markers were found to be sufficient in order to adequately represent population genetic structure of this insect in the sampled regions [39]. Structure 2.2 analyses clearly depict two genetically distinct clusters of D. saccharalis present in the southern United States (Figure 2). The presence of two distinct clusters was confirmed using the ΔK statistic of Evanno et al. [42]. Diatraea saccharalis from southern Texas, eastern Texas and Louisiana grouped together, whereas individuals from Florida belong to a genetically distinct cluster. Our data show no evidence of interbreeding or migration between the two genetic clusters, suggesting that the Florida population of D. saccharalis is a distinct genotype and possibly a cryptic species. Of the 96 alleles produced by the AFLP reactions, 24 were present only in Texas and Louisiana, while 14 alleles were unique to the Florida population.

Bottom Line:
Two molecular markers, AFLPs and mitochondrial COI, were used to examine genetic variation among these regional populations and to compare the sequences with those available in GenBank and BOLD.We found geographic population structure in the southern United States which suggests two introductions and the presence of a previously unknown cryptic species.Management of D. saccharalis would likely benefit from further investigation of population genetics throughout the range of this species.

Affiliation:
SNRI, University of California Merced, Merced, California, United States of America.

ABSTRACTThe sugarcane borer moth, Diatraea saccharalis, is widespread throughout the Western Hemisphere, and is considered an introduced species in the southern United States. Although this moth has a wide distribution and is a pest of many crop plants including sugarcane, corn, sorghum and rice, it is considered one species. The objective was to investigate whether more than one introduction of D. saccharalis had occurred in the southern United States and whether any cryptic species were present. We field collected D. saccharalis in Texas, Louisiana and Florida in the southern United States. Two molecular markers, AFLPs and mitochondrial COI, were used to examine genetic variation among these regional populations and to compare the sequences with those available in GenBank and BOLD. We found geographic population structure in the southern United States which suggests two introductions and the presence of a previously unknown cryptic species. Management of D. saccharalis would likely benefit from further investigation of population genetics throughout the range of this species.